! common 传递变量
program main

    implicit none
    common/cm/a, b
    integer :: a, b
    external :: set_value

    call set_value()
    print *, a, b

end program main

impure subroutine set_value()
    integer :: a, b
    common/cm/a, b

    a = 1
    b = 2

end subroutine set_value
